A fuel tank with a filter formed of a fluororesin element has conventionally been known (e.g., see Japanese Utility Model Laid-Open Publication No. HEI-4-123364). The fuel tank disclosed in this publication will be described with reference to FIG. 21.
Referring to FIG. 21, an overflow passage 202 is formed around a filler cap 201. In a portion connecting the overflow passage 202 to a fuel tank 203 is provided a fuel reservoir 204 for temporarily holding fuel overflowing through a fluororesin filter 205. The overflow passage 202 has a drain hole 206 through which to let rainwater out.
Fuel overflowed when fuel is fed into the fuel tank 203 is separated by the fluororesin filter 205 into water and fuel. Fuel passes through the filter 205 and is collected through the fuel reservoir 204 in the fuel tank 203. On the other hand, water such as raindrops passes through the drain hole 206 and is discharged into a drain passage 207.
However, since the filter 205 is disposed in parallel with the bottom of the drain passage 207, water remaining in the overflow passage 202 can cover the top surface of the filter member 205. If water covers the filter 205, the water film will exert a blocking effect, preventing passage of fuel, and making smooth filtration impossible.
Therefore, desired is a fuel tank which can smoothly filter fuel containing water, over a long period of time.
Also, a fuel tank with a filter (or a strainer) provided in a fuel filler hole of a fuel tank body has been known (e.g., Japanese Patent Laid-Open Publication No. 2003-83187). The fuel tank disclosed in this publication will be described with reference to FIG. 22.
A fuel filler hole 302 is provided at the top of a tank body 301 shown in FIG. 22. A strainer 303 is provided in the filler hole 302, and the filler hole 302 is covered by a cap 304. The strainer 303 is attached to one end of a string body 305, and a stopper 306 is attached to the other end thereof.
The strainer 303 includes a plurality of openings 308 formed in a side wall 307 and another portion, and a metal mesh 309 attached to the openings 308 for catching and filtering out foreign matter.
The string body 305 is prevented from being pulled out above a certain level from the tank body 301 by the stopper 306. Since the cap 304 and the strainer 303 are connected to the one end of the string body 305, the strainer 303 and the cap 304 are prevented from falling off the tank body 301 or being lost.
When fuel is injected, the metal mesh 309 attached to the strainer 303 can catch foreign matter in the fuel. However, water contained in the fuel cannot be separated.
Fuel contaminated with water accumulates in the fuel tank, or can cause the problem that it enters an engine and its induction system.
To deal with this, a sump and a drain plug are generally provided at the bottom of the fuel tank body to remove water accumulated on the bottom as appropriate. However, it is not easy to detect the presence and the amount of water and other matter accumulated in the tank.
To detect the presence and the amount of water and other matter, it has been proposed to provide a viewing window at the fuel tank. However, the addition of a drain plug and a viewing window leads to an increase in product cost.
Therefore, there is a desire for a fuel tank which can separate water and other matter entering the fuel tank over a long period of time, and can facilitate checking the amount of separated water, at low cost.
For another example, Japanese Utility Model Laid-Open Publication No. SHO-55-10543 discloses a fuel tank with a fluororesin element having the property of not allowing water to pass through it but allowing fuel to pass through it, so as to separate water contained in the fuel from the fuel. The fuel tank disclosed in this publication will be described in detail with reference to FIG. 23.
As shown in FIG. 23, a fuel feeding pipe 403 connects a fuel tank 401 to a fuel pump 402, and a fluororesin element 404 is provided inside the fuel tank 401 in such a manner as to enclose a fuel suction opening 403a of the fuel feeding pipe 403. Reference numeral 405 denotes a drain valve provided at a bottom portion 401a of the fuel tank 401.
Fuel in the fuel tank 401 is sucked through the fuel suction opening 403a by the fuel pump 402. At that time, water contained in the fuel is separated by the fluororesin element 404 which encloses the fuel suction opening 403a, and accumulates on the bottom portion 401a. Water accumulated on the bottom portion 401a is let out through the drain valve 405, and thus water in the tank 401 is removed.
To remove water accumulated in the fuel tank 401, a sump and the drain valve 405 provided at the bottom portion 401a are opened and closed as appropriate. However, it is difficult to detect the presence and the amount of water accumulated in the tank 401. In order to detect the presence and the amount of water, a viewing window is provided at the fuel tank in some cases. However, the addition of a drain plug and a viewing window leads to an increase in product cost.
Thus, there is a demand for a fuel tank with a filtration mechanism of a simple configuration and which can be manufactured at low cost which can facilitate checking water separated 5 by filtration and allows removal of water.